Abstract
The wide distribution of Wolbachia in all major classes of arthropods and filarial nematodes evidence the ability of this heritable endosymbiont to switch horizontally between species boundaries. Several laboratory-studies where Wolbachia was successful transferred artificially by microinjection showed that Wolbachia is able to adapt to new genetic hosts backgrounds. However, there is still a lack of examples on the course of horizontal transfer in nature. Here the Wolbachia-infections of Rhagoletis cerasi are compared to those of the recently introduced Rhagoletis cingulata. Strain characterization by MLST and wsp showed that European and American R. cingulata specimens are infected with wCin2, a strain ident to wCer2 of R. cerasi. Additionally some of the European individuals are infected with wCin1, a strain ident to wCer1. wCin1 was never found in the USA and thus it is likely that European populations acquired this strain after their introduction to Europe from R. cerasi. Quantification of wCin1 and wCin2 by qPCR showed that wCin1 positively influences wCin2 titers. Our study system allows novel insights into the dynamics of interspecific Wolbachia transfer at an early stage.